Advances in electronics technology are leading to ever-smaller device designs with an ever-increasing variety of applications. Many "computing" devices, including handheld computers, Personal Digital Assistants ("PDA"), pagers, and cellular phones, are now small enough to be easily carried or even worn.
Highly miniaturized computing devices, such as handheld computers and PDAs, have significant operational limitations as a consequence of their small size. In particular, the computer-human interface is highly constrained: the small size greatly restricts possible approaches for data input. Traditional desktop computer-human interfaces, those that rely on keyboards and pointing devices, translate poorly to very small devices. Typically, PDAs lack a keyboard. Some handheld computer designs attempt to mimic desktop computer designs, however, only a miniature keyboard can be included.
In response to this problem, these computing devices generally provide for data input through a stylus and/or a limited number of buttons. Other miniature portable devices, such as pagers and cellular phones, typically rely on buttons for command input.
Newer approaches to the computer-human command submission interface have the goal of improving the interface for computers of all sizes. One approach is to employ tilt and/or translation sensors to achieve an alternate means of data input. In "Inertial Proprioceptive Devices: Self-Motion-Sensing Toys and Tools" by C. Verplaetse, IBM Systems Journal, Vol. 35, pg. 639 (1996), the author describes devices that are able to sense and react to their own position and orientation through use of embedded inertial motion sensors. The author further describes commercially available accelerometers and gyroscopes for use as inertial motion sensors in portable computing devices.
An implementation of the position and orientation sensing approach to data input is described in "Design of Spatially Aware Graspable Displays", by David Small and Hiroshi Ishii, CHI 97, pg. 367. The authors describe a large handheld or table positioned device that can be used to read a "newspaper" or other written document. Tilting of the device, in an intuitive manner, provides input commands for scrolling up or down, and left or right through the document: the graphical display responds to the angular orientation of the device. Translating the device closer to or further from the body of the user controls zooming of the document, in effect, scrolling in a third dimension. A button provides a "clutch" to lock and unlock the response of the display to user commands.
A much smaller prototype handheld device that also makes use of tilt for data input is described in "Tilting Operations for Small Screen Interfaces (Tech Note)" by Jun Rekimoto, UIST 1996, pg. 167 (1996). This device employs a combination of: 1) tilting for input of scrolling commands to move through text or an image; and 2) button pushing for input of activating commands for navigation through the display of text or to view a portion of an image in greater detail.
In addition to the problem of command input, small electronic devices typically must maximize the convenience of their portability and physical accessibility. Portable devices typically must be carried in a pocket, a bag, or by hand. During use, they typically must be held in a hand or placed on a surface while the fingers of the other hand provide data entry. This reduces the convenience of the portability of the computer, cellular phone, etc. Some physical designs provide for a wearable computer to improve portability and usability. U.S. Pat. No. 5,416,730, "Arm Mounted Computer" issued to Eric S. Lookofsky on May 16, 1995, provides for a three-sectioned computer which mounts to the forearm of the user with data entry via a keyboard. This approach frees one hand during operation of the device without requiring the device to be placed, for example, on a tabletop. U.S. Pat. No. 5,305,181, "Arm or Wrist Mounted Terminal with a Flexible Housing" issued to Darald R. Schultz on Apr. 19, 1994, similarly provides a wrist-mounted device with keyboard data entry and a display. U.S. Pat. No. 5,587,577, "Modular Scanner with Hand-Held Data Terminal" issued to Darald R. Schultz on Dec. 24, 1996, provides for a scanner unit mounted to the back of the hand/wrist as part of an inventory scanner device. Such wearable designs have the drawback of interfering with clothing and/or requiring the user to hold the arm in an awkward position during use.
In summary, the existing approaches for wearable device placement and data input have several difficulties. Operation and viewing the display screen can be awkward. The device can interfere with clothing. Further, such wearable devices continue to have the requirement of the use of fingers, typically via buttons or a stylus, for input of at least some types of commands and inconvenient positioning on a body and occupation of one or both hands of the user during command input. What is therefore desired is a wearable device with easy and conveniently positioned access that can readily use motion sensors for finger-free command input.